update docs

Author: rez1dent3

docs/_sidebar.md

@@ -28,7 +28,12 @@
     - [Refund](refund)
     - [Gift](gift)
     - [Cart](cart)
-    
+
+- Transactions
+
+    - [Transaction](transaction) 
+    - [Race condition](race-condition) 
+
 - Additions
 
     - [Wallet Swap](laravel-wallet-swap)

docs/race-condition.md

@@ -0,0 +1,38 @@
+## Race Condition
+
+A common issue in the issue is about race conditions.
+
+If you have not yet imported the config into the project, then you need to do this.
+```bash
+php artisan vendor:publish --tag=laravel-wallet-config
+```
+
+Previously, there was a vacuum package, but now it is a part of the core. You just need to configure the lock service and the cache service in the package configuration `wallet.php`.
+
+```php
+    /**
+     * A system for dealing with race conditions.
+     */
+    'lock' => [
+        'driver' => 'array',
+        'seconds' => 1,
+    ],
+```
+
+To enable the fight against race conditions, you need to select a provider that supports work with locks. I recommend `redis`.
+
+There is a setting for storing the state of the wallet, I recommend choosing `redis` here too.
+
+```php
+
+    /**
+     * Storage of the state of the balance of wallets.
+     */
+    'cache' => ['driver' => 'array'],
+```
+
+You need `redis-server` and `php-redis`.
+
+Redis is recommended but not required. You can choose whatever the [framework](https://laravel.com/docs/8.x/cache#introduction) offers you.
+
+It worked! 

docs/transaction.md

@@ -0,0 +1,37 @@
+## Transaction
+
+Sometimes you need to execute many simple queries. You want to keep the data atomic. To do this, you need `laravel-wallet` v7.1+.
+
+It is necessary to write off the amount from the balance and raise the ad in the search. What happens if the service for raising an ad fails? We wrote off the money, but did not raise the ad. Received reputational losses. We can imagine the opposite situation, we first raise the ad in the search, but it does not work to write off the money. There are not enough funds. This functionality will help to solve all this. We monitor ONLY the state of the wallet, the rest falls on the developer. Let's take an unsuccessful lift, for example.
+
+```php
+use Bavix\Wallet\Internal\Service\DatabaseServiceInterface;
+
+/** @var object $businessLogicService */
+/** @var \Bavix\Wallet\Models\Wallet $payer */
+$payer->balanceInt; // 9999
+app(DatabaseServiceInterface::class)->transaction(statuc function () use ($payer) {
+    $payer->withdraw(1000); // 8999
+    $businessLogicService->doingMagic($payer); // throws an exception
+}); // rollback payer balance
+
+$payer->balanceInt; // 9999
+```
+
+Now let's look at the successful raising of the ad.
+
+```php
+use Bavix\Wallet\Internal\Service\DatabaseServiceInterface;
+
+/** @var object $businessLogicService */
+/** @var \Bavix\Wallet\Models\Wallet $payer */
+$payer->balanceInt; // 9999
+app(DatabaseServiceInterface::class)->transaction(statuc function () use ($payer) {
+    $payer->withdraw(1000); // 8999
+    $businessLogicService->doingMagic($payer); // successfully
+}); // commit payer balance
+
+$payer->balanceInt; // 8999
+```
+
+It worked!